This specification relates to data compression techniques for encoding and decoding image data. Image data can be encoded and decoded by a number of different techniques that use block-based coding processes. One example technique is the H.264 video compression standard. In such processes, an image or a frame of a video is divided into blocks and the blocks are spectrally transformed into coefficients, quantized, and entropy encoded. In some cases, the data being transformed are not the actual pixel data, but are residual data following a prediction operation. The predictions can be intra-frame, i.e. block-to-block within the frame/image, or inter-frame, i.e. between frames (also called motion prediction).
Like reference numbers and designations in the various drawings indicate like elements.